Expected Equivalent Magnetic Noise Spectral Density of Magnetoelectric Composites as Magnetic sensors: From Theory to Experiments

Abstract

ABSTRACTWith the development of applications involving high sensitivity ferromagnetic-ferroelectric laminates, a systematic analysis of the noise floor for magneto-electric (ME) laminated sensor has become crucial. We report and discuss the results of such an analysis on the noise floor of magnetostrictive-piezoelectric laminates in terms of the magnetic noise spectral density at room temperature. The noise floor of highly sensitive ME laminates with a JFET charge amplifier detection method has been studied. A good correlation was found between the theoretical and experimental noise curves within the measurement bandwidth. The dominating noise sources were found to include the dielectric loss noise, mechanical loss noise of the magneto-electric laminates and the noise sources of the charge amplifier. By using an appropriate low noise JFET charge amplifier, the noise contributions from the amplifier can be made negligible, enabling the measurement of the intrinsic noise of the ME laminates sensor. Thus, we have shown that at low frequencies, below the resonant frequency, the dielectric loss noise predominates with a one-per-root-frequency dependence whereas, around the resonance, the mechanical loss noise prevails over all other noise sources as expected from our theoretical analysis.